Today, OLED devices have gradually become the mainstream in the display field. OLED devices present excellent characteristics, such as a low power consumption, a high color saturation, a wide viewing angle, a thin thickness and being available for flexible display, etc.
Generally, a color display of an OLED device may be realized by sub-pixels independently emitting red, green and blue (RGB) light, or through a white-light emitting OLED used in combination with color filters. Currently, the independent RGB-light emitting sub-pixels are the commonly used color display design used in many OLED devices.
An OLED is powered by the driving current. A control circuit composed of a plurality of thin film translators (TFTs) and capacitors is generally configured for each sub-pixel. The control circuit is configured to supply a stable current to a light emitting unit of the sub-pixel to control light emission. Because the control circuit occupies a rather large pixel area, in order to reduce the circuit disconnection risks between the control circuit and the light emitting unit, pixel defining layer materials are used to fill via holes of the pixels. To further keep the storage capacitance of the control circuit, a metal layer may also be added. However, the above improvements and other factors may reduce the aperture ratio of a pixel, thereby decreasing the resolution of the OLED display panel.